EHIZOPUS 107 



THE ALGA-LIKE FUNGI, OR PHYCOMYCETES 



106. Rhizopus nigricans (Mucor stolonifer), the bread mold** 

 (App. 15). A culture is easily obtained by placing a slice of 

 bread on a rack, or other support, inside a bell jar set in a dish 

 of water to form a moist chamber. 



A. Note the gradual development of mold over the substratum 

 (bread), and the color and size of the filaments, or hyphce, 

 which together constitute the mycelium. Is the mycelium 

 all above the surface of the bread ? Observe the develop- 

 ment of upright stalks, in groups, and the black sporangia 

 formed at their ends. Is the direction of the growth of the 

 hyphse above the surface of the bread influenced by light ? 



B. Lift off carefully some of the mycelium and mount in 

 water. Note under m.p. the color and structure of a hypha. 

 Is it septate ? What alga does it resemble in cell structure 

 except for the absence of chloroplasts ? Draw under h.p- 

 a tip showing the cell wall and distribution of the proto- 

 plasm. Observe the glistening globules of oil or fat, and 

 watch for streaming movements. Material stained with 

 haematoxylin (Sec. 182) will demonstrate the very numerous 

 minute nuclei. Is the filament a coenocyte ? 



C. Mount portions of the mycelium with groups of stalks 

 beajring sporangia (sporangiophores). Draw a group of stalks 

 about five times its natural size. Note and draw under m.p. : 



1. The base of a group, showing a cluster of root-like fila- 

 ments, rhisoids, that penetrate the substratum. 



2. Stages in the development of the sporangium, showing 

 (a) the enlargement of the end of the filament before the 

 formation of the dome-shaped columella, which cuts off the 

 terminal sporangium ; (b) a sporangium containing develop- 

 ing spores, and showing the position of the columella. 



3. The end of a stalk (sporangiophore) after the rupturing 

 of the sporangium wall, exposing the columella. 



4. A group of spores under h.p. 



